THE EXPERIMENTAL DEMONSTRATION OF PRE‐MIGRATION ACTIVITY IN THE ABSENCE OF FAT DEPOSITION IN BIRDS

Abstract

Summary.Under dietary conditions that experimentally prevented the accumulation of “pre‐migratory” depot fat, typical nocturnal migratory restlessness developed in the Brambling Fringilla montifringilla. Subsidiary data are presented from Junco hyemalis and Zonotrichia albicollis.In captive controls, the rapid accumulation and subsequent utilization of body fat closely paralleled the onset and waning of nocturnal unrest.Although the Brambling accumulates fat reserves before both nuptial and contra‐nuptial flights, it would seem that the presence of such is not an essential element of the so‐called “total physiological state” necessary for the onset of migration.